Program Director/Principal Investigator (Last, First, Middle): Beidas, Rinad Sary The proposed study will work to reduce firearm-related suicide deaths in young people by investigating the most effective way to implement a universal safe firearm storage program in pediatric primary care. The number of young people dying by suicide in the United States continues to rise, and risk for suicide death is much greater when there is an unlocked, loaded firearm in the home. A simulation study found that a modest increase in safe firearm storage could prevent up to 32% of firearm-related deaths in youth. Pediatric primary care is an ideal setting for universal suicide prevention strategies to reduce access to firearms, and prior research has shown that both health care clinicians and parents find firearm safety to be an appropriate topic to discuss, yet these conversations do not happen routinely. Safety Check, an evidence-based practice for firearm safety promotion that involves brief counseling and provision of a free cable lock, has been shown to double the odds of self-reported safe storage among parents but has not been implemented widely. Using feedback from pediatric clinicians, health system leaders, and firearm-owning parents regarding attitudes and barriers related to broader use of the program, the proposed study incorporates recommendations on how to boost the acceptability and feasibility of Safety Check for use as a universal suicide prevention strategy. Combining this feedback with insights from behavioral economics, we will conduct a hybrid type III effectiveness-implementation with a longitudinal cluster randomized design. The study will allow us to compare two approaches to implementing the program in pediatric primary care and evaluate the effectiveness of the adapted intervention, now named Gun Safe. The study will include 151 clinicians in 32 clinics who serve 38,989 youth annually in two MHRN health systems in Michigan and Colorado. All 32 clinics in the two participating health systems will receive Gun Safe materials, including brief training and cable locks. Half of the clinics (k = 16) will be randomized to receive the EHR implementation strategy (Nudge); the other half will be randomized to receive Nudge plus 1 year of facilitation to target additional clinician and organizational implementation barriers (Nudge+). We will collect the primary implementation outcome for 6 months before exposure to condition and for 1 year following to allow for comparisons between (a) the active and pre- exposure periods and (b) the active and sustainment periods. Results will guide future efforts to promote firearm safety as a universal suicide prevention strategy. In Aim 1, we will identify the effect of the implementation strategies on implementation outcomes (i.e., parent-reported clinician fidelity, reach (how many families received the intervention), cable lock distribution, acceptability, and cost). In Aim 2, we will also test potential implementation strategy mechanisms (i.e., how it worked). In Aim 3, we will examine clinical outcomes including a parent-reported safe storage behavior. This study can improve implementation of firearm safety interventions and identify the best approach to national implementation, with the ultimate goal of saving the lives of American youth, in alignment with NIMH Objective 4.